1. Field of the Invention
The invention relates to completion of bore holes. In one aspect, the invention relates to recompletion of an open hole bore hole so as to isolate a permeable zone in a subterranean formation from other permeable zones in the subterranean formation. In a more specific aspect, the invention relates to recompletion of an open hole well bore of a production well that had been stimulated by detonation of high explosives so as to make the recompleted well suitable for injection of a fluid in a fluid drive process, for example, in an enhanced oil recovery process involving injection of carbon dioxide (CO.sub.2).
2. Brief Description of the Prior Art
The following, among other things, comprises a prior art statement in accordance with the guidance and requirements of 37 CFR 1.5, 1.97, and 1.98.
There are situations when it is advantageous to recomplete an open hole well bore so as to establish fluid communication between the well bore and a permeable zone of a subterranean formation to the exclusion of communication with other permeable zones in the subterranean formation.
An example of a situation in which such recompletion is highly advantageous is in the implementation of an enhanced oil recovery process involving injection of a fluid from an injection well into a permeable subterranean formation containing residual hydrocarbons, so as to cause the hydrocarbons to migrate to a production well, with production of the hydrocarbons or oil to the surface from the production well. More specifically, after depletion by primary production, and even after water flooding, is completed, it is often advantageous to institute an enhanced oil recovery process involving injection of CO.sub.2 into injection wells and production of displaced hydrocarbons from production wells.
Primary production is often from open hole completions. That is, a casing is set from the surface to near the production horizon, the casing is cemented into place, and then the well is drilled and completed open hole, without casing, to depth. To stimulate production, it is common practice in many reservoirs to detonate high explosives such as nitroglycerin in the well bore at selected sites near subterranean zones of high permeability that produce hydrocarbons or oil. This is often effected where there are numerous production horizons so as to make sure that all producible zones are opened for production. Thus, high rates of production are obtained, and there is little chance of missing a zone of potential production, which might be true if a cased hole were perforated at intervals indicated to be productive, as by well logs.
The foregoing procedure works fine as long as primary production lasts. However, there comes a time with all reservoirs when primary production becomes uneconomic. When this occurs, very large amounts of unrecovered oil may still be left in the reservoir. At such time, it is often advantageous to institute an enhanced oil recovery process, for example, involving injection of CO.sub.2 into production wells and recovery of displaced oil from production wells.
In the development of such an enhanced oil recovery process, considerable savings of time, energy, and funds involved with drilling new wells can be realized if open hole well bores having zonal breakdown in the locus of the well bore can be reconstituted so as to isolate permeable zones of interest from other permeable zones in the subterranean formation. This has heretofore not been feasible, particularly when the open zones were blasted with nitroglycerin or other high explosives. Greatly added expenses of drilling new patterns of new injection wells were required.
The process of the invention is advantageous for effecting considerable savings by recompleting such open hole production wells for conversion to injection wells for use in such fluid drive processes.
It is known in the prior art to form permeable sheaths of "synthetic permeable rock" around well bores so as to mitigate sand production. It is also known to squeeze thermosetting resin and particulate material through perforations into cavities in a formation, and then to drill out the plug in the well, after setup, so as to mitigate sand production problems. Specifically, U.S. Pat. No. 3,929,191 is exemplary of a process wherein epoxy resin or phenolic resin coated sand grains are squeezed through perforations in a casing into cavities in a formation, the mixture is allowed to set up into a consolidated permeable synthetic rock-like mass under influence of heat from the subterranean formation, the plug in the well is drilled out, and the permeable plugs in the cavities are left in place to mitigate sand production.
Relating in another way to the invention, U.S. Pat. No. 3,918,522 is exemplary of prior art disclosing isolating formations by casing, cementing, and then perforating into the zone of interest.
It is apparent, however, that this procedure is not feasible when the zone of interest has been broken down by blasting or sand production, since the cement squeezed into the cavity would be difficult or impossible to perforate.
The inventors are also aware of U.S. Pat. No. 3,542,132; U.S. Pat. No. 3,999,608; U.S. Pat. No. 3,107,727; U.S. Pat. No. 3,209,823; U.S. Pat. No. 3,336,980; U.S. Pat. No. 3,708,013; U.S. Pat. No. 3,709,298; and U.S. Pat. No. 3,929,191, which are cumulative to the references specifically discussed above, or which show the state of the art as applying to one step or another of the inventive sequence of steps comprising the process claimed in this application.
However, none of the references suggest or make obvious the obtaining of the new result obtained by the steps of the process claimed herein.